1. Field of the Invention
The present invention relates to a method of driving an organic EL device and a display device which can prolong a lifetime of luminance, can prevent the elevation of a drive voltage or the increase of a drive current at the time of driving of the organic EL device with a fixed current.
2. Description of Related Art
An organic EL device, in general, has the structure in which an organic thin film containing a light emitting layer is sandwiched by an anode and a cathode, and by applying a DC voltage to the organic EL film, holes are injected from the anode and electrons are injected from the cathode thus emitting light. When the balance of electrons and holes is collapsed due to the influence of the charge transfer and the energy barrier of the materials which constitute these layers, the charge stored stage continues. Due to a portion of the charge stored in the organic thin film, the organic material is degenerated or the structure of the organic layer is changed. Such degeneration of the organic material and change of the structure of the organic layer has been one of causes of the deterioration of the organic EL device.
In Japanese Laid-open publication 2000-30862 (patent document 1), there exists a description that by driving a single-layered or stacked-layered organic EL device by applying a sinusoidal AC voltage between an anode and a cathode and by periodically changing the voltage applied to the device so as to periodically repeating an ON state (emission of light) and an OFF state (non-emission of light) of the device, the deterioration is recovered at the OFF state thus prolonging a driving lifetime.
In Japanese Laid-open publication 2000-36383 (patent document 2), there exists a description that by driving a single-layered or stacked-layered organic EL device by applying a pulse voltage of frequency of 5 kHz or more between an anode and a cathode and by setting the frequency at the time of performing this pulse driving to 5 kHz or more, a recovery effect of the deterioration at the time of OFF state is increased and hence, the deterioration of the device is suppressed.